void OnUpdateUI(object sender, EventArgs e)
        {
            Command command = CreateCommand();

            if (command != null)
            {
                CommandButtonUIState state = new CommandButtonUIState(this);
                command.UpdateUIState(state);
            }
        }
        void OnUpdateUI(object sender, EventArgs e)
        {
            if (button == null)
            {
                return;
            }

            Command command = CreateCommand();

            if (command != null)
            {
                CommandButtonUIState state = new CommandButtonUIState(button);
                command.UpdateUIState(state);
            }
        }